Adjustable propeller



April 1945. w. L. EFFINGER, JR

ADJUSTABLE PROPELLER Filed May 11, 1943 3 4 (Z iii INVENTOR.

v M/ILL/AMLOu/S EFF/NGERi/A. I

A TTORNEX Patented Apr. 3, 1945 UNITED STATES PATENT OFFICE ADJUSTABLE PROPELLER William Louis Eflinger, Jr., West Hempstead, N. Y. Application May 11, 1943, Serial No. 486,493 5 Claims. (cairn-160) My invention is an improvement in propellers which are particularly adapted for use in model airplanes, although the constructions involved render it adaptable for use in connection with boats, fans and other devices. panying drawing, I have illustrated the best form in which I have contemplated embodying the invention, together with a slight modification thereof, and the said invention is fully disclosed inthe following description and claims. The

structures illustrated in the accompanying drawa ing are particularly; adapted for use in connection with model airplanes and for convenience will be described with reference thereto. g

In the accompanying drawing,

Fig. 1 is a view illustrating the parts of my improved propeller separated fromeach other for convenience of description.

' Fig. 2 is a sectional view of one of the blades .on the IineZ- -Z of 1.

Fig. 3 is aview partly in section showing the complete propeller assembled.

' Fig. 4 is a sectional view taken on the line 4-4 of Fig. 3 through one end of the hub.

Fig. 5 is a, sectional view of one ofthe blades taken onthe line 5-5 f Fig.3. W

Fig. 6 is a similar section of the blade on the line 6--6. of'Fig. 3.

Fig. 7 is a similar sectional view of the blade on the line 1-7 of end.

Fig. 8 is a partial view of a modification in which a different form of hub is employed in connection with three blades similar to those shown in Fig. 3.

Fig. 9 is a detailed view of the hub of the propeller shown in Fig. 8.

Figs. 10, 11 and 12 are detailed views showing a section of one of the propeller blades in adjusted positions for varying'the pitch thereof.

Referring now to the construction of the propeller, I represents the propeller hub which is preferably of general cylindrical form and is provided at its opposite ends with inwardly tapered recesses 2-2. The hub I is also provided with a central assage 3 to receive the driving shaft of the propeller. The propeller blades are indicated at l-4, and each is provided with a hub engaging portion 4a, having tapered sides, as indicated at 4b, the said hub engaging portion being of slightly greater width than the portion of the blade immediately extending outwardly therefrom, it being understood that the hub engaging portion will be flexed into curved form so as to fit within one of the tapered recesses In the accom- Fig. 3 adjacent to its outer .Z. in. which it may be secured. by means of a plug 5, as clearly shown in Fig. 3. The main body of each blade 4 is of the usual propeller blade form, and the portion indicated at 40 adjacent to the leading edge 411 is slightly narrower than the portion 4e on the opposite side H of the longitudinal axis of the blade, as clearly versely curved throughout the main portions of shown in Fig. 1. When the hub engaging portions of the blade are inserted in the tapering recess 2 of the hub, the blades will be transthe length of the blade to different extents as indicated in Figs. 5, 6 and 7, the transverse curvature of the blade being greatest adjacent to the hub portion and gradually flattened toward the outer end of the blade to accommodate the different peripheral speeds of the blades from the hub engaging portion to the outer end of blades where obviously the peripheral speed will be greatest. It will be readily understood that the pitch of each blade can be alteredby partially rotating the hub engaging portion 4a in the recess 2 which it engages, so as to vary the pitch as desired, and this can be done by loosening plug or removing it, after which the plug is reinserted firmly so as to lock each blade in its adjustedposition. Figs. 10, 11 and 12 illustratethe variations in the position of the blade under various adjustments of the pitch thereof.

The pitch may be canged in order to obtain the.

desired or maximum performance. Obviously, low pitch gives fast climb. High pitch gives long, fast flight and medium pitch gives best all around performance of the propeller. In adjusting the propeller blades in the respective recesses 2, the eccentricity of the said recesses will assist in securing the desired adjustment of the blades.

A particular advantage of this construction is that especially in the application of it to model airplanes the adjustment of the propeller blades obtains the best results desired and can be readily accomplished in the manner previously described, after which the relation of the blades to the hub may be made permanent by securing the plugs 5 within the recesses 2 by gluing them or by the use of any other desired fastening In Figs. 8 and 9 I have illustrated a modification of the invention in which the hub indicated at llll is provided with three or more tapering recesses lll2to receive an equal number of propeller blades constructed in the manner shown in Figs. 1 to 7 and previously described, the blades being indicated in Fig. 8 at I 4. The hub IN is provided with an axial passage therethrough indicated at N13 for the passage of the propeller shaftand the blade, receiving recesses I02 will beequally distributed-around the axis of the aperture. The method of adjusting the individual blades of the propeller will be the same as hereinbefore described.

In carrying out my invention .the .prop'eller blades may be formed of any suitable sheetmaterial, but I have found in practice 'that'for use in model airplanes it is desirable to formztherblades of tough, resilient, stiff paper, such as ,fibreboard or bristol board. This material is inexpensive and The, hub is, preferably formed ofewood,- hutmay if desired to. be made.of.-.meta l, plastic oro.ther suitable material.

- What, I claim and; desire totsecure why-Letters Patent is:

1. The herein described mo.del:-.propel1er1com-. prising. a streamlined-hub havingizinwardlyz'tapered blade receiving recesses, mpropeller .zblades formed from fiat sheet material and eachhaving a curved hub engaging portionsfor. engaging-one of said recesses in the hub and frictionally held" therein to permit theblades to'be rotated in-said recesses to vary the pitch oisaid blades, and :in- Wardly tapering plugs *coaxial withsaid recesses for engaging the-curved hub engaging portion of each blade and r'eleasably lookingit with respect to the hub.

2. In a propeller fora model airplane; thecombination *of a hub? having an inwardly-tapered .Jprising a hub provided with inwardly tapered blade receiving recesses and a plurality of blades formed from inherently flat, flexible sheet material having hubengaging portions flexed into position to fit within one of said tapered recesses ,andlxtoz-be .frictionally held in position therein to permit each blade to be adjusted rotarily within its tapered recesses in the hub to vary the pitch -of: .the,blade, .and .a tapered plug-removably fit- :tingwithin the hub. engaging; portions of .each

blade 'for releasably locking-the blade vin adrjusted position with respect to the. hub.

;;4...In1 a model-propllergthe combination .of a

:hub, :provide'd .with an inwardly :tapered blade M receivingrecess: of circularecross section; an. inawardly;taperedcircular;plugii-fitting into saidyrecess: and-.a'piblade iformedzzofsinherentlyyflat. re-

silient sheet material: 'andt'havvingea: hub-:portion adapted .tolbe held -between said plug-and the wallet-said -recess,- said blade being-flexed and --held in curved position-against 'theresiliency of causing the transverse'ciu'vature of, the blade .to

vary inversely to 'thejdistance; from ,the. hub.

5. In-..a v.propellerfor iasmodel airplane, the combination of a hub havingran'inwardlytapered radial blade receiving recess, aninwardly tapered plug fitting into said-recess, landfa. blade; formed f inherently. fiat, resilient-fibrous sheet material,

:-.position by engagement ofcaachub portion: of; the

blade between said plug 'a-n'd the -1wall of said recess.

WILLIAM LOUIS ,EFFINGER, JR. 

